Have you bothered to read the full link provided by ku4hx?
How to use it is right there:
Use the bootable installer
Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:
Apple silicon
- Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing. A bootable installer doesn't download macOS from the internet, but it does require an internet connection to get firmware and other information specific to the Mac model.
- Turn on the Mac and continue to hold the power button until you see the startup options window, which shows your bootable volumes.
- Select the volume containing the bootable installer, then click Continue.
- When the macOS installer opens, follow the onscreen installation instructions.
Intel processor
- Plug the bootable installer into a Mac that is connected to the internet and compatible with the version of macOS you're installing. A bootable installer doesn't download macOS from the internet, but it does require an internet connection to get firmware and other information specific to the Mac model.
- Turn on your Mac, then immediately press and hold the Option (Alt) key.
- Release the Option key when you see a dark screen showing your bootable volumes.
- Select the volume containing the bootable installer. Then click the onscreen arrow or press Return.
- If you can't start up from the bootable installer, make sure that Startup Security Utility is set to allow booting from external or removable media.
- Choose your language, if prompted.
- Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.